When you choose "inject / apply translation", one of the options in the dialog that opens is "Word Wrap by Tags". You need to configure this to get translator++ to wrap long lines of text to new lines.
For RPGM games, you'll typically need to configure two word wrap settings, one for text with a face picture, and one for text on its own. The "maximum length" values (i.e., how wide can the text be without going off screen) you'll have to play around with to find the right number, since it will depend on how exactly the game is configured.